Add reliable inbound sync controller

Author: Marcus Pousette

.changeset/clean-inbound-sync.md

@@ -0,0 +1,5 @@
+---
+'@treecrdt/sync': minor
+---
+
+Add an inbound sync helper with aggregate per-target failures, cancelling timeouts, and live filter subscriptions.

packages/treecrdt-sync/README.md

@@ -34,6 +34,24 @@ Use `addTarget` only when the transport was already attached to the same `localP
 dedupes standard TreeCRDT `Operation` values by `meta.id`. Pass `opKey` only for a custom op shape
 or custom coalescing behavior.
 
+## Multi-peer inbound sync
+
+Use `createInboundSync` to reconcile or subscribe the same filters across registered peer
+transports. `syncOnce` resolves only when every requested peer/filter target succeeds. If any target
+fails, it finishes the remaining targets and rejects with `InboundSyncAggregateError`; its
+`failures` entries identify the `peerId`, `filter`, and original `error` for each failed target.
+
+```ts
+const inbound = createInboundSync({ localPeer: peer });
+inbound.addPeer('remote:server', websocketTransport);
+
+await inbound.syncOnce({ all: {} }, { syncTimeoutMs: 10_000 });
+inbound.subscribe([{ children: { parent: rootId } }]);
+```
+
+A `syncTimeoutMs` deadline aborts the underlying `SyncPeer.syncOnce` session, so reconciliation does
+not keep sending after the caller receives the timeout failure.
+
 ## When not to
 
 - You only need the protocol types and `SyncPeer` (use **`@treecrdt/sync-protocol`**).